Pittsburgh Ballet Theatre company pianist Yoland Collin plays Etudes by Virgil Thomson as the company dances "Drink to Me Only with Thine Eyes" by Mark Morris through March 17 at the August Wilson Center. The dance program "Unspoken" also includes Balanchine's "Serenade" and Tudor's "Lilac Garden." The Belgian-born pianist speaks about Thomson's seldom-heard Etudes, which are delightful, folk-infused gems.